Aircraft with electric or hybrid electric propulsion and aerodynamic braking implemented by the rotor of an electric machine and engine group for such an aircraft

Abstract

A drive unit (18), such as an intelligent motor, comprises an electronic control unit (20) and an electric machine (22). The electronic control unit is configured to selectively operate the electric machine in a propulsion mode and in an aerodynamic braking mode. In the latter mode, the electronic control unit is configured to control the torque T of the electric machine as a function of the rotational speed N of its rotor (22B) according to a polynomial control law, where "n" is a natural number greater than or equal to 2, and is a set of numerical coefficients, the coefficient of order n being strictly negative. The use of a polynomial law allows for stable operation and is not dependent on the reliability of sensors external to the drive unit, such as airspeed sensors on an aircraft. Figure for the abstract: Figure 1

Description

Title of the invention: Aircraft with electric or hybrid electric propulsion and aerodynamic braking implemented by the rotor of an electric machine and motor group for such an aircraft. Technical field

[0001] The present invention relates to the general field of electrically or hybrid-electrically propelled aircraft.

[0002] It relates more particularly to an optimization of a propulsion system of such an aircraft for the implementation of aerodynamic braking by a propeller in flight, which in certain embodiments can be coupled to an energy storage unit to recharge the latter and thus implement regenerative braking.

[0003] The invention is the result of technological research aimed at developing the use of electrical technologies to provide aircraft propulsion, and thus contributes to reducing their environmental impact and to combating climate change. Prior art

[0004] The principle of propelling aircraft by means of electric motors driving rotating propellers or fans, alone in electric propulsion systems, or combined with thermal engines in hybrid propulsion systems, is known.

[0005] The use of electric or hybrid propulsion systems in aircraft offers numerous advantages, including the possibility of implementing regenerative braking during certain phases of flight. Such regenerative braking involves using an aircraft's electric motor in generator mode, that is, ensuring that the aerodynamic force applied to the propeller due to the aircraft's forward movement through the air results in a torque applied to the motor's rotor in the opposite direction to the rotor's rotation, thereby producing electrical energy and storing it in a battery. In other words, it involves using the propulsion system in wind-powered mode.

[0006] Such a capability makes it possible, in particular, to increase the flight range of aircraft and improve aircraft maneuverability by reducing the duration of descent, approach, and landing phases thanks to the braking effect of the propulsion system. In cases where the maximum permissible speed of such an aircraft is limited by the mechanical characteristics of the propeller or the fan coupled to the electric motor (and not by other parts of the aircraft), reducing the rotational speed of the electric motor by means of regenerative braking also makes it possible to reduce the risk of propeller overspeed and thus increase the maximum permissible speed of the aircraft.

[0007] More generally, whether or not the aim is to recharge an energy storage unit, the possibility of operating an aircraft's electric motor in generator mode offers the option, by coupling it to an electrical load, of implementing aerodynamic braking of the aircraft using the propeller. This makes it possible to effectively reduce the aircraft's speed during approach and landing phases. Such aerodynamic braking is particularly advantageous in the case of small aircraft with a relatively high lift-to-drag ratio, which can make it difficult to slow the aircraft down during the approach phase.

[0008] The implementation of such aerodynamic braking, whether or not it is accompanied by the recharging of an energy storage unit, nevertheless poses difficulties in controlling the electric motor in a way that allows for stable operation of the propulsion system and therefore of the aircraft. Furthermore, it is desirable that the piloting of the aircraft, in particular the control of propulsive power or the intensity of aerodynamic braking, depending on the flight phases, be simple and intuitive for the pilots. Description of the invention

[0009] The invention aims in particular to enable aerodynamic braking implemented by the rotor of an electric machine, allowing stable and safe operation.

[0010] The invention provides for this purpose an aircraft engine assembly, comprising an electric machine and an electronic control unit, the electric machine comprising a stator and a rotor, the electronic control unit being configured to selectively operate the engine assembly in: • a propulsion mode, in which the electronic control unit supplies the electric machine with electrical energy and commands it to operate as a motor, so as to drive the rotor in rotation; and • an aerodynamic braking mode, in which the electronic control unit commands the electric machine to operate as a generator so as to generate electrical energy under the effect of a rotation of the rotor.

[0011] In aerodynamic braking mode, the electronic control unit is configured to control the torque T of the electric machine as a function of the rotor's rotational speed N according to a polynomial control law T(N) = A₀ + A] x N + ... Aₙ x N, where "n" is a natural number greater than or equal to 2, and {A₀ ... Ars] is a set of numerical coefficients, the coefficient Aₙ being of order n being strictly negative.

[0012] Using a polynomial law is equivalent to controlling the electric machine so that it behaves essentially like a fan, resulting in particularly stable operation. Furthermore, the control of the electric machine is thus independent of information provided by sensors independent of the motor unit, such as aircraft airspeed sensors, and is therefore not dependent on the reliability of such sensors.

[0013] The present invention thus proposes a safe, simple, stable, robust and easily implementable control principle.

[0014] In some embodiments, the control unit and the electric machine are integrated, for example within the same housing, so as to form a self-contained assembly of the type commonly called an "intelligent motor" or, in English, a "smart motor".

[0015] In preferred embodiments, the integer n is equal to 2.

[0016] In preferred embodiments, the coefficient Ao is strictly positive.

[0017] Such a positive coefficient Ao ensures that from a minimum rotor speed threshold, the torque T becomes a driving force again so that the engine unit switches back to propulsion mode and thus prevents the rotor speed from falling below this minimum threshold.

[0018] Such an arrangement is particularly advantageous in cases where the electric machine is a sensorless speed-controlled machine using an estimator, as explained for example in document FR2954020A1. Indeed, such a speed estimator requires that the rotor's rotational speed remain above a certain threshold, so as not to risk a loss of control of the machine.

[0019] In preferred embodiments, the electronic control unit is configured to assign different sets of values ​​to the set of coefficients { Ao... An} as a function of an aerodynamic braking setpoint level.

[0020] In preferred embodiments, the electronic control unit is configured such that at least some of the sets of values ​​attributable to the set of coefficients { ... An} define corresponding control laws. tively to curves which, on a diagram representing the torque T as a function of the rotational speed N, cover a continuous region of control laws intended to be implemented in response to aerodynamic braking commands, up to a curve corresponding to a "FULL" command for maximum aerodynamic braking.

[0021] In preferred embodiments, the electronic control unit is configured so that another of the sets of values ​​attributable to the set of coefficients ficients {. A„} defines a control law, intended to be implemented in response to a "SLOW" instruction for maximum deceleration of the propeller, and corresponding to a curve located outside said region and separated from the latter by a region in which are located respective minima of propeller curves.

[0022] The invention also relates to an aircraft, comprising an engine group of the type described above, a propeller coupled to the rotor of the electric machine, and an electrical load configured to store or dissipate the electrical energy generated by the electric machine in the aerodynamic braking mode.

[0023] In this disclosure, the term "propeller" is used to refer to both a propeller and a blower.

[0024] In preferred embodiments, the aircraft includes an energy storage unit configured to power the electric machine through the electronic control unit in propulsion mode, and constituting said electrical load, whereby the aerodynamic braking mode is a regenerative braking mode in which the engine group recharges the energy storage unit from the energy generated by the electric machine.

[0025] In preferred embodiments, the aircraft includes a thrust lever configured to selectively provide a thrust command or an aerodynamic braking command to the electronic control unit, the latter being configured to operate the engine group in propulsion mode in response to said thrust command, and to operate the engine group in aerodynamic braking mode by controlling the torque T of the electric machine according to said polynomial control law, in response to said aerodynamic braking command.

[0026] In preferred embodiments, the electronic control unit is configured to modify all or part of the coefficients {. An} of the polynomial control law in response to a modulation of a level of the aerodynamic braking setpoint caused by a movement of the thrust lever within an adjustment zone.

[0027] In preferred embodiments, the adjustment area includes a "REV" range for progressively increasing the level of aerodynamic braking, from a "0" position corresponding to a zero braking setpoint, to a "FULL" position corresponding to said "FULL" setpoint for maximum aerodynamic braking, and a "SLOW" position corresponding to said "SLOW" setpoint for maximum propeller deceleration.

[0028] The invention also relates to a method for implementing an aircraft of the type described above, comprising: • the provision of a thrust command to the electronic control unit, whereby the electronic control unit supplies the electric machine with electrical energy and commands it to operate as a motor, so as to drive the rotor and thus the propeller in rotation; and • the provision of an aerodynamic braking command to the electronic control unit, whereby the latter controls the electric machine, according to said polynomial control law, to operate as a generator so as to generate electrical energy under the effect of a rotation of the rotor driven by the propeller.

[0029] The invention also relates to a computer program product comprising code instructions for executing the steps of the process defined above, when said program is executed on an electronic control unit. Brief description of the drawings

[0030] The invention will be better understood, and other details, advantages and features thereof will become apparent from the following description, given by way of non-limiting example and with reference to the accompanying drawings in which:

[0031] [Fig-1] is a schematic view of an electrically propelled aircraft according to a mode preferred implementation of the invention;

[0032] [Fig.2] is a diagram illustrating curves representing the torque T as a function of the rotational speed N of a propeller of the aircraft of [Fig.1], in stabilized regime respectively for different conventional speeds of the aircraft;

[0033] [Fig.3] is a diagram similar to [Fig.2], further illustrating curves representing control laws of the regenerative torque T as a function of the rotational speed N of the propeller, corresponding respectively to different operating instructions;

[0034] [Fig.4] is a schematic top view of a thrust lever of the aircraft of [Fig.1], Detailed presentation of preferred embodiments

[0035] Fig. 1 illustrates very schematically an electrically powered aircraft 10, whose propulsion system 12 includes an electric load 14, an electric power bus 16, at least one motor group 18, and a propeller 24. The electric load 14 is, in the preferred example shown, an energy storage unit, typically comprising at least one electrochemical battery.

[0036] The motor group 18 comprises an electronic control unit 20 and an electric machine 22. The electronic control unit 20 typically comprises an electrical converter. The electric machine 22 comprises a stator 22A, and a rotor 22B coupled by an output shaft to propeller 24.

[0037] In the illustrated example, propeller 24 is a fixed-pitch propeller.

[0038] The energy storage unit 14 is connected to the electric machine 22 via the power supply bus 16 and the electronic control unit 20 so that, in a propulsive operating mode, the energy storage unit 14 supplies the electric machine 22 via the electronic control unit 20 so that the electric machine 22, then operating as a motor, drives the propeller 24 in rotation, while, in a regenerative operating mode, the energy storage unit 14 is recharged by an electric current produced by the electric machine 22, then operating as a generator, under the effect of a drive of the rotor 22B by the propeller 24. This latter operating mode aims to allow regenerative braking in flight and thus generally offer the advantages described above.

[0039] For this purpose, the converter of the electronic control unit 20 is configured to operate as an inverter in the propulsion operating mode, so as to convert a direct current DC, from the energy storage unit 14 and routed by the power supply bus 16, into an alternating current AC suitable to power the electric machine 22, typically a three-phase current.

[0040] Furthermore, the converter of the electronic control unit 20 is configured to operate as a rectifier in the regenerative operating mode, so as to convert an alternating current AC produced by the electric machine 22 operating as a generator, into a direct current DC suitable for recharging the energy storage unit 14.

[0041] The motor group 18 includes, for example, a housing within which the components of the group, including the electronic control unit 20 and the electric machine 22, are brought together in such a way as to form an assembly commonly referred to as a "smart motor" or "intelligent motor".

[0042] Although the present detailed description relates to an example in which the energy supplied by the electric machine 22 operating as a generator is collected (in the energy storage unit 14), the invention is also applicable in cases where the electrical load is configured to dissipate this energy without storing it. In such a case, the corresponding operating mode is not a regenerative braking mode but, more generally, an aerodynamic braking mode.

[0043] A specific feature of the present invention lies in a control law for the electric machine 22 by the electronic control unit 20 in the phases of regenerative braking, or more generally of aerodynamic braking, in this case a control law for the resistive torque developed by the electric machine to generate electrical energy by opposing the rotation of the propeller 24.

[0044] To facilitate understanding of what follows, the diagram in [Fig. 2] shows propeller curves C1-C4 of the propulsion system 12, i.e., curves of torque T (in Newton-meters Nm) as a function of rotational speed N (in revolutions per minute RPM), respectively for different conventional speeds (in knots kn) of the aircraft. "Conventional speed," also referred to as KCAS for "Knot Calibrated Air Speed," is understood to be the indicated airspeed of the aircraft, corrected for position and instrument errors, and therefore equal to the true airspeed under standard atmospheric conditions at sea level. It should be noted that this diagram only shows the portion of the propeller curves corresponding to generator operation (negative torque T and positive speed N), and therefore omits the portion corresponding to propulsion operation (positive torque T and positive speed N).

[0045] On each of the curves C1-C4, the respective point P1-P4 located where the curve intercepts the x-axis (zero torque T) corresponds to a speed stabilization point when no driving or braking force is applied to the propeller shaft 24.

[0046] Beyond points P1-P4, each of the curves C1-C4 shows what value of torque T stabilizes the propeller speed N as a function of the value of said speed N, for a given conventional aircraft speed. Generally, for a given speed N, a torque T greater than that given by the curve tends to induce an acceleration of the propeller 24, while a torque T less than that given by the curve tends to induce a deceleration of the propeller. This is explained by the fact that increasing the torque T is equivalent to decreasing the resistance to the rotation of the propeller 24 induced by the electric machine 22, i.e., decreasing the resistive torque, while reducing the torque T is equivalent to increasing this resistance.

[0047] Each propeller curve C1-C4 has a respective minimum M1-M4 that determines the minimum torque Tlmin-T4min (i.e., the maximum resistive torque) applicable to the propeller and the corresponding speed Nlmin-N4min. In practice, given the concave shape of each propeller curve around its minimum M1-M4, the maximum power that can be generated (dissipated or collected) during braking for a given propeller curve is obtained at a speed slightly higher than the speed Nlmin-N4min for which the torque T is minimal.

[0048] For each curve, it is noteworthy that for speeds N lower than the speed corresponding to the considered minimum M1-M4, the system remains naturally unstable. Indeed, with a simple control law that would consist of adjusting the torque T to satisfy a speed setpoint N, it appears that in the speed range close to the considered minimum M1-M4, there would be no preferred direction for maintaining the speed: an increase in the torque T would randomly lead to either an increase or a decrease in the speed N. Moreover, in the In the zone of speeds N lower than the speed corresponding to the minimum M1-M4 considered, an increase in the torque T (i.e. a reduction in the resistive torque) from a given operating point P, normally intended to accelerate the propeller, will in reality have the effect of slowing down the propeller by following the curve C1-C4 considered in the direction of decreasing speeds N.

[0049] Another possible control law could consist of controlling the electric motor 22 according to a torque setpoint T. However, such a control method presents the risk that a setpoint corresponding to a resistive torque that is too strong (i.e., of too high an absolute value), given the conventional speed of the aircraft, may cause the propeller to stop, and thus compromise the control of the motor and therefore of the aircraft.

[0050] The present invention proposes a simple, stable, robust and easily implementable control principle, which will now be described.

[0051] This principle generally consists of configuring the electronic control unit 20 so as to control the electric machine 22 according to a polynomial control law of the torque T as a function of the rotational speed N, that is to say such that T(N) = Aq + Af x N + ... An x N”, “n” being a natural number greater than or equal to 2, and the coefficient An (of order n) being strictly negative (since, by convention, a positive torque T corresponds to a motor torque while a negative torque T corresponds to a resistive torque).

[0052] The coefficients {Aq... A„} are numerical coefficients that can be fixed. However, in the preferred example shown, the electronic control unit 20 is configured to assign different sets of values ​​to the set of coefficients {Ao ... A„} depending on the level of an aerodynamic braking setpoint, for example, regenerative braking, as will become clearer below. Furthermore, the coefficients {Ao ... A„} are preferably defined by respective continuous functions of the braking setpoint level within a determined braking setpoint range.

[0053] In the preferred example described, the law is of order 2, that is, such that T(N) = +A] x N +A, x N2-

[0054] The use of a polynomial law amounts to controlling the electrical machine 22 so that it behaves substantially like a fan, which allows stable operation.

[0055] The inventors have indeed noticed that the helix curve visible in [Fig.2] has characteristics similar to those of an operating curve of an asynchronous motor, with in particular: - at zero speed, a starting torque; - a maximum torque point; - beyond the point of maximum torque, a drop in torque in the high-speed region, resulting in zero torque.

[0056] However, asynchronous machines have stable operating speeds when associated with fan-type loads, the latter behaving according to polynomial laws.

[0057] Figure 3 is a diagram similar to Figure 2 but also showing L1-L4 curves of the torque T as a function of the velocity N according to the second-order polynomial law specified above, respectively for different sets of values ​​of the set of coefficients { Aq... An}.

[0058] The curve L1 delimits a continuous region R of control laws which are defined by the coefficients [ Ao... An} determined by the aforementioned continuous functions when the braking setpoint level sweeps the determined braking setpoint range, and which are intended to be implemented in response to aerodynamic braking setpoints, in this case regeneration setpoints.

[0059] In particular, the L1 curve defines a control law intended to be implemented in response to a maximum braking command, referred to as "FULL" hereafter. The L1 curve intersects the propeller curves at points slightly offset to the right with respect to the minima M1-M4 and therefore close to the points where the power generated is maximum. On this L1 curve, the propeller 24 thus operates with high efficiency in wind power mode, which makes it possible to maximize aerodynamic braking and, in the illustrated embodiment, to maximize the recharging of the energy storage unit 14.

[0060] The region R is thus defined above the curve Ll on the [Fig.3].

[0061] Curves L2 and L3 are two examples of control laws corresponding to less intense regeneration instructions than the maximum regeneration defined by the LL curve. The two curves L2 and L3 are thus in the R region. The determined braking instruction range, on which the aforementioned continuous functions operate which allow the coefficients {Ao ... A„} to be defined as a function of the braking instruction level, typically extends from a zero braking instruction level up to the "FULL" maximum braking instruction level.

[0062] Curve L4 defines a control law intended to be implemented in response to a maximum deceleration command for the propeller 24, referred to as "SLOW" hereafter. This control law is defined so as to implement aerodynamic or regenerative braking that best reduces the speed of the propeller 24 without risking the shutdown of the electric motor 22. The SLOW command is advantageous in the context of a multi-engine aircraft equipped with a fixed-pitch propeller capable of being put into flag, or of an aerobatic aircraft, or even of a vertical takeoff aircraft for which it may be necessary to reduce the propeller speed to a minimum in the event of the loss of an opposing engine.

[0063] The L4 curve is located outside the R region and separated from it by a MIN region in which are located the respective minima of the propeller curves 24, for example the M1-M4 minima of the C1-C4 curves. Preferably, no control law is defined in the MIN region, so as to avoid certain braking level commands corresponding to two possible control laws on either side of a corresponding Mx minimum (one in the R region and the other in the MIN region), which would complicate control from the pilot's point of view.

[0064] For each of the control laws thus defined, the coefficient A) is advantageously strictly positive, which results in a positive torque T (i.e., a driving torque) at the lowest propeller rotation speeds N, tending to re-accelerate the propeller 24 and thus reducing the risk of uncontrolled engine stalling. The coefficient A) is, for example, the same for the different control laws. The transition from one law to another within region R, or between region R and curve L4, is thus achieved by changing all or part of the coefficients A and A2.

[0065] Figure 4 illustrates a thrust lever 30 intended to allow an aircraft pilot to control the thrust of the engine group 18. More specifically, the lever 30 is rotatable along an angular stroke, for example, delimited by an opening 32 provided in a housing 34, continuously in an adjustment zone 36, on the front side, corresponding to a range of positive thrust setpoints to propel the aircraft, and in an adjustment zone 38, on the rear side, corresponding to a range of aerodynamic braking setpoints, in this case regenerative braking, passing through an adjustment notch "0" corresponding to a zero propulsion setpoint without aerodynamic braking, which may correspond to freewheeling operation, operation under a zero torque setpoint, or a setpoint with a positive torque heel in the manner of the positive heel defined by the coefficient A) as explained above.

[0066] A movement of the thrust lever 30 in the adjustment zone 38 allows a level of the aerodynamic braking setpoint to be modulated and thus cause a modification of all or part of the coefficients {A) • ■ • A} of the control law implemented by the electronic control unit 20.

[0067] More specifically, the adjustment zone 38 includes a "REV" range of progressive increase of the level of aerodynamic braking, going from the "0" position up to a "FULL" position corresponding to the aforementioned "FULL" braking setpoint, followed by a position or notch corresponding to the "SLOW" setpoint aimed at slowing down the propeller 24 as much as possible without risking stopping the electric motor 22.

[0068] It must therefore be understood that when the push lever 30 is positioned in its "REV" range or in the "FULL" position at the limit of the "REV" range, the electric machine 22 is controlled according to a control law belonging to the region R of [Fig.3], or, where applicable, corresponding to the "FULL" setting associated with the curve L1 of [Fig.3].

[0069] Similarly, when the push lever 30 is positioned on the "SLOW" notch, the electric machine 22 is controlled according to a control law corresponding to the curve L4 of [Fig.3].

[0070] In the illustrated example, moving the push handle 30 into the adjustment zone 38 (i.e. below the notch "0") therefore has the effect of modifying all or part of the coefficients Aj and A2.

[0071] In general, the thrust lever 30 thus allows simple and intuitive control of the propulsion system 12, similar to a classic thrust control from the point of view of the pilots.

[0072] In the described example, the torque T of the electric motor is determined by the converter of the electronic control unit 20. However, the manner in which the converter implements the control law is not the subject of this disclosure. The operation of the converter is based, for example, on conventional control techniques, such as vector control techniques. A method of configuring the converter 20 to control the torque T can be found in EPI document 138539B1.

[0073] Furthermore, the electric machine 22 can be of the type controlled without a speed sensor, from an estimator, as explained for example in document FR2954020. As explained above, such a speed estimator requires that the rotational speed of the rotor 22B remain above a certain threshold, otherwise control of the machine may be lost.

[0074] The coefficient A) is preferably a strictly positive number chosen to ensure that the rotational speed of the rotor 22B remains above this minimum threshold and thus avoid a loss of control of the electric machine 22.

[0075] In such a case, the "SLOW" position plays a role as a safety setting insofar as such a setting offers a minimum speed allowing the pilot to considerably reduce the speed of the propeller 24 while avoiding an uncontrolled stoppage of the electric machine 22, which would result in particular in a loss of the rotor speed estimate.

Claims

Demands

1. Aircraft engine assembly (18), comprising an electric machine (22) and an electronic control unit (20), the electric machine (22) comprising a stator (22A) and a rotor (22B), the electronic control unit (20) being configured to selectively operate the engine assembly (18) in: • a propulsion mode, in which the electronic control unit (20) supplies the electric machine (22) with electrical energy and commands the latter to operate as a motor, so as to drive the rotor (22B) in rotation; and • an aerodynamic braking mode, in which the electronic control unit (20) commands the electric machine (22) to operate as a generator so as to generate electrical energy under the effect of a rotation of the rotor (22B);characterized in that, in the aerodynamic braking mode, the electronic control unit (20) is configured to control the torque T of the electric machine (22) as a function of the rotational speed N of the rotor (22B) according to a polynomial control law T(N) = Ao + Aj XN + ... An x N", "n" being a natural number greater than or equal to 2, and { Ao... An} being a set of numerical coefficients, the coefficient An of order n being strictly negative.;

2.

3. Engine group according to claim 1, in which n is equal to 2. Engine group according to claim 1 or 2, in which the coefficient Ao is strictly positive.

4. Engine group according to any one of claims 1 to 3, wherein the electronic control unit (20) is configured to assign different sets of values ​​to the set of coefficients {Ao ... A„} as a function of an aerodynamic braking setpoint level.

5. Engine group according to claim 4, wherein the electronic control unit (20) is configured such that at least some of the sets of values ​​attributable to the set of coefficients {Ao ... Aw} define corresponding control laws respec- tively to curves (L1, L2, L3) which, on a diagram representing the torque T as a function of the rotational speed N, cover a continuous region (R) of control laws, intended to be implemented in response to aerodynamic braking instructions, up to a curve (L1) corresponding to a "FULL" instruction of maximum aerodynamic braking.

6. Engine group according to claim 5, wherein the electronic control unit (20) is configured such that another set of values ​​attributable to the set of coefficients defines a control law, intended to be implemented in response to a "SLOW" instruction for maximum deceleration of the propeller (24), and corresponding to a curve (L4) located outside said region (R) and separated from the latter by a region (MIN) in which are located respective minima (M1-M4) of curves (C1-C4) of the propeller (24).

7. Aircraft, comprising an engine group (18) according to any one of claims 1 to 6, a propeller (24) coupled to the rotor (22B) of the electric machine (22), and an electrical load (14) configured to store or dissipate the electrical energy generated by the electric machine (22) in the aerodynamic braking mode.

8. Aircraft according to claim 7, comprising an energy storage unit configured to power the electric machine (22) via the electronic control unit (20) in propulsion mode, and constituting said electrical charge (14), whereby the aerodynamic braking mode is a regenerative braking mode in which the engine group (18) recharges the energy storage unit from the energy generated by the electric machine (22).

9. Aircraft according to claim 7 or 8, comprising a thrust lever (30) configured to selectively provide a thrust command or an aerodynamic braking command to the electronic control unit (20), the latter being configured to operate the engine group (18) in propulsion mode in response to said thrust command, and to operate the engine group (18) in aerodynamic braking mode by controlling the torque T of the electric machine (22) according to said polynomial control law, in response to said aerodynamic braking command.

10. Aircraft according to claim 9, wherein the engine group (18) is an engine group according to claim 4 or 5, and the electronic control unit (20) is configured to modify all or part of the coefficients- ficients { Ao... An ) of the control law in response to a modulation of a level of the aerodynamic braking setpoint caused by a movement of the thrust lever (30) within an adjustment zone (38).

11. Aircraft according to claim 10, wherein the engine group (18) is an engine group according to claim 6, and wherein the adjustment zone (38) comprises: • a “REV” range of progressive increase of the level of aerodynamic braking, going from a “0” position corresponding to a zero braking instruction up to a “FULL” position corresponding to said “FULL” instruction of maximum aerodynamic braking, and • a “SLOW” position corresponding to said “SLOW” instruction of maximum deceleration of the propeller (24).

12. A method of implementing an aircraft according to any one of claims 7 to 11, comprising: • providing a thrust command to the electronic control unit (20), whereby the electronic control unit (20) supplies the electric machine (22) with electrical energy and controls the latter to operate as a motor, so as to drive the rotor (22B) and thus the propeller (24) in rotation; and • providing an aerodynamic braking command to the electronic control unit (20), whereby the electronic control unit (20) controls the electric machine (22), according to said polynomial control law, to operate as a generator so as to generate electrical energy under the effect of a rotation of the rotor (22B) driven by the propeller (24).

13. Product computer program comprising code instructions for carrying out the steps of the process according to claim 12, when said program is executed on an electronic control unit (20).

Images